KR102245883B1 - Method and device for the production of a polymer melt containing additives and blowing agents - Google Patents

Abstract

In a method and apparatus for preparing an additive/blowing agent containing polymer melt (P _AT ), a first polymer melt (P ₁ ) and a second polymer melt (P ₂ ) are provided. At least one additive (A) and said first polymer melt (P ₁ ) are mixed with a screw machine (8) to obtain an additive-containing polymer melt (P _{A ).} In addition, at least one blowing agent (T) and a second polymer melt (P ₂ ) are mixed by a mixing device (41) to obtain a blowing agent-containing polymer melt (P _{T ). A} blowing agent-containing polymer melt P _T is added to the additive-containing polymer melt P A provided in the screw machine 8. In order to obtain an additive/blowing agent-containing polymer melt (P _AT ), the blowing agent-containing polymer melt (P _T ) and the additive-containing polymer melt (P _A ) are mixed with a screw machine (8).

Description

TECHNICAL FIELD The method and apparatus for producing a polymer melt containing an additive and a blowing agent TECHNICAL FIELD

The present invention relates to a method and apparatus for preparing a polymer melt, in particular a polystyrene melt, containing an additive and a blowing agent.

One method for preparing polymer melts containing additives and blowing agents is known from WO 2009/052 898 A1. The polymer melt is provided by a polymerization reactor and fed into the screw machine. In a first step, at least one additive and then at least one blowing agent are mixed into the polymer melt in a screw machine. To this end, the screw machine has an additive supply port and a blowing agent supply port arranged downstream thereof to mix at least one additive and at least one blowing agent, and the blowing agent supply port and the additive supply port are each mixing It is related to the domain. Then, the polymer melt containing the additive and blowing agent is pelletized to form expandable or expanded polymer pellets. When mixing at least one additive and at least one blowing agent, mechanical energy is introduced into the polymer melt. The energy so introduced needs to be removed from the polymer melt by a screw machine in a complicated process so that the temperature of the polymer melt is kept below the critical decomposition temperature of the at least one additive.

It is an object of the present invention to provide a method for preparing a polymer melt containing an additive and a blowing agent in a simple manner.

The above object is achieved in accordance with the present invention with a method for preparing a polymer melt containing an additive/blowing agent, the method comprising the steps of: providing a first polymer melt and a second polymer melt; Mixing the first polymer melt with at least one additive with a screw machine to obtain an additive-containing polymer melt; Mixing the second polymer melt with at least one blowing agent to obtain a blowing agent-containing polymer melt; Adding the blowing agent-containing polymer melt to the additive-containing polymer melt provided in the screw machine; And mixing the blowing agent-containing polymer melt and the additive-containing polymer melt with the screw machine to obtain an additive/blowing agent-containing polymer melt. In order to prepare a polymer melt containing an additive and a blowing agent, at least one additive is mixed into the first polymer melt by means of a screw machine, so that the additive-containing polymer melt is provided in the screw machine. The at least one blowing agent is mixed into the second polymer melt outside of the screw machine, in particular by means of a mixing device, so that the polymer melt containing the blowing agent is provided outside of the screw machine. The polymer melt consists in particular of the same polymer material, in particular polystyrene. And the blowing agent-containing polymer melt is added to the additive-containing polymer melt provided in the screw machine. Then, the blowing agent-containing polymer melt and the additive-containing polymer melt are mixed by a screw machine to obtain an additive/blowing agent-containing polymer melt. Upon exit from the screw machine the additive/blowing agent-containing polymer melt is preferably pelletized.

In the method according to the invention, mixing at least one additive is separate from mixing at least one blowing agent, so that the temperature of the polymer melt containing the additive or the polymer melt containing the additive/blowing agent is more easily adjusted and monitored. can do. Mixing of the at least one blowing agent into the second polymer melt can be carried out without the need to monitor the critical decomposition temperature of the at least one additive. Mixing at least one blowing agent reduces the viscosity and temperature of the second polymer melt, so that the blowing agent-containing polymer melt can be easily mixed into the additive-containing polymer melt. When the viscosity is lowered, the mechanical energy input required for mixing is reduced, so that the temperature of the additive/blowing agent-containing polymer melt can more easily be maintained below the critical decomposition temperature.

The blowing agent-containing polymer melt is preferably cooled before being added to the additive-containing polymer melt. The polymer melt containing the blowing agent can absorb the relatively high cooling power introduced by the melt cooler, in particular. If necessary, the temperature of the additive-containing polymer melt or the additive/blowing agent-containing polymer melt is adjusted by a cooling process carried out in the screw machine. Since the blowing agent-containing polymer melt is preferably cooled before being added to the additive-containing polymer melt, less cooling is required in screw machines.

Suitable polymers or polymer melts are, for example, polystyrene, polyethylene, polypropylene and mixtures of these polymers. Other suitable polymers include those based on renewable raw materials such as polylactide and biodegradable polymers such as cellulose acetate. Additives suitable for mixing in the polymer melt are, for example, flame retardants, cell modifiers, graphite, carbon black, talc and/or colorants. Blowing agents suitable for mixing in the polymer melt are pentane, in particular hydrocarbons such as n-pentane or iso-pentane, alcohols, carbon dioxide, nitrogen or mixtures of these compounds.

Depending on the type of polymer and at least one blowing agent selected, depending on the pelletizing method, both expandable polymer pellets and expanded polymer pellets can be prepared. The expandable polymer pellets are preferably prepared by an underwater pelletizing method, and the expanded polymer pellets are preferably prepared by a water ring pelletizing method. According to the continuous process according to the invention, expandable and/or already expanded polymer pellets can be produced with high polymer throughput. The second polymer melt is preferably provided by a polymerization reactor and supplied to a mixing device by a melt pump, in which the second polymer melt is mixed with at least one blowing agent. The method according to the invention can also be further refined to have the features described in claims 10 to 15.

The polymer melt containing the additive/blowing agent has a polymer weight ratio (a _s ) and the polymer weight ratio (a ₁ ) of the first polymer melt is a ₁ <0.4·a _S , especially a ₁ <0.3·a _S , also in particular a ₁ The <0.2·a _S method provides a simple way to prepare a polymer melt. The first polymer melt has a first polymer weight ratio (a ₁ ). Correspondingly, the second polymer melt has a second polymer weight ratio (a ₂ ). When the polymer weight ratio (a ₁ , a ₂ ) is added, the polymer weight ratio (a _s ) of the polymer melt containing the additive/blowing agent is obtained, a ₁ + a ₂ = a _s . Thus, a ₂ /a ₁ Rain is a ₂ /a ₁ > 3/2, especially a ₂ /a ₁ > 7/3, also especially a ₂ /a ₁ >4. Thus, at least one additive is _{mixed in a much smaller weight ratio (a 1} ), and at least one blowing agent is mixed in _{a larger weight ratio (a 2 ).} The weight ratio (a _s ) defines the total polymer melt without at least one additive and at least one blowing agent. As the at least one additive is _{mixed in a smaller weight ratio (a 1} ), it is relatively easy to keep the temperature of the additive-containing polymer melt below the critical decomposition temperature, and in particular the amount of cooling required is relatively small. Because of the relatively low viscosity, the mechanical energy input when mixing the polymer melt containing the blowing agent is low, and thus the amount of cooling required during mixing to keep the temperature of the polymer melt containing the additive/blowing agent below the critical decomposition temperature is relatively small. do.

Before adding at least one additive (A), the first polymer melt has a temperature (T ₁ ), which temperature (T ₁ ) is T ₁ <185°C, in particular T ₁ <175°C, and in particular T ₁ <165°C. The phosphorus method provides a simple way to mix at least one additive. The first polymer melt is in particular cooled before adding at least one additive. The first polymer melt can in particular be provided according to different methods. In the first method, the screw machine is loaded with polymer pellets, which are melted in a melting zone before the at least one additive is mixed. The first polymer melt is cooled in the melting zone, in particular by means of cooling. In a second method, the first polymer melt is removed from the polymerization reactor and passed through a melt cooler for cooling by a melt pump. The cooled first polymer melt is then fed to the screw machine, where it is delivered to a first mixing zone where at least one additive is mixed into the first polymer melt. In the third method, the provided blowing agent-containing polymer melt is divided into a first partial stream and a second partial stream. The first partial stream is supplied to the screw machine by a melt pump disposed upstream of the first mixing zone in which at least one additive is mixed. In this screw machine, the first partial stream is preferably removed of volatile components by means of a rear discharge so that at least one of the mixed blowing agents can escape, so that a first polymer melt free of blowing agents is provided. The temperature of the first polymer melt is preferably measured with a temperature sensor and monitored with a control device.

The method in which the first accumulation region of the first polymer melt is formed prior to mixing the at least one additive with the screw machine provides a simple way of mixing the at least one additive. At least one accumulating member is provided on the at least one processing element axis to form the first accumulating region. The at least one accumulating member is configured such that the conveying direction of the accumulating member is opposite to the conveying direction of the screw machine. The first polymer melt accumulates in the first accumulation region to form a melt seal. This melt seal prevents the volatile components of the additive-containing polymer melt from flowing in the upstream direction. Since the first accumulation region formed upstream of the outlet allows volatile components to escape through the outlet, the melt seal provides a simple way to remove volatile components, especially from the additive-containing polymer melt. The at least one additive is in particular selected from the group comprising for example flame retardants, cell modifiers, graphite, carbon black, talc and/or colorants. The critical decomposition temperature (T _K ) of the _{at least one additive is T K} ≥ 240°C, in particular T _K ≥ 210°C, and in particular T _K ≥ 180°C.

The method in which the volatile component is liquefied in the additive-containing polymer melt while mixing at least one additive provides a simple method of mixing the at least one additive. Volatile components that escape from the additive-containing polymer melt during mixing are discharged through the outlet. This outlet is preferably formed upstream of the supply port for supplying at least one additive.

Before adding the blowing agent-containing polymer melt, the additive-containing polymer melt has a temperature (T ₂ ), and this temperature (T ₂ ) is T ₂ <195 °C, especially T ₂ <185 °C, and especially T ₂ <175 °C. The method provides a simple way to prepare a polymer melt. While the at least one additive is being mixed, the temperature of the additive-containing polymer melt does not exceed the critical decomposition temperature. If necessary, the additive-containing polymer melt is cooled during mixing, so that unwanted temperature increases due to mechanical energy introduced during mixing are avoided. For cooling, screw machines are provided with cooling, in particular in the mixing zone. The temperature of the additive-containing polymer melt is preferably measured with a temperature sensor and monitored with a control device.

After mixing at least one additive and before adding the blowing agent-containing polymer melt, the method in which a second accumulation region is formed into the additive-containing polymer melt by means of a screw machine comprises: a blowing agent-containing polymer melt and an additive-containing polymer melt. It provides a simple way to mix. To prevent the at least one volatile blowing agent from escaping from the blowing agent-containing polymer melt or the additive/blowing agent-containing polymer melt, a first accumulation region consisting of the additive-containing polymer melt is upstream of the inlet for the blowing agent-containing polymer melt. It is formed on a screw machine. To form the second accumulation region, at least one processing element axis has at least one accumulation member. This at least one accumulating member has a delivery direction opposite to that of the screw machine. The additive-containing polymer melt accumulates to form a melt seal in the second accumulation region. This melt seal allows the amount of blowing agent that escapes during the mixing of the polymer melt containing the blowing agent and the polymer melt containing the additive to flow upstream and exit the screw machine through the outlet and/or inlet.

When fed into the screw machine 8, the blowing agent-containing polymer melt has a temperature (T ₃ ) and this temperature (T ₃ ) is T ₃ <180°C, especially T ₃ <170°C, and in particular T ₃ The <160°C method provides a simple method of mixing the blowing agent-containing polymer melt and the additive-containing polymer melt. When mixing the polymer melt containing the blowing agent and the polymer melt containing the additive, mechanical energy is introduced by the screw machine, resulting in an increase in temperature. The temperature of the blowing agent-containing polymer melt, despite this temperature increase, ensures that the temperature of the additive/blowing agent-containing poly and the melt does not exceed the critical decomposition temperature in the mixing zone. In the second mixing zone, the screw machine is in particular provided with a cooling section. If necessary, the cooling section cools the additive/blowing agent-containing polymer melt so that the temperature increase due to the input of mechanical energy is kept below the critical decomposition temperature.

The method of cooling the polymer melt containing the blowing agent before being fed into the screw machine, in particular with a melt cooler, provides a simple way to prepare the polymer melt. _{By cooling the blowing agent-containing polymer melt, the critical decomposition temperature (T K} ) is not exceeded when the blowing agent-containing polymer melt is mixed with the additive-containing polymer melt. When mixing with a screw machine, mechanical energy is introduced into the polymer melt containing the additive/blowing agent, resulting in an increase in temperature. When the blowing agent-containing polymer melt is cooled, the temperature of the additive/blowing agent-containing polymer melt does not exceed the critical decomposition temperature during and after mixing, despite the increase in temperature. The melt cooler can introduce relatively high cooling power to the blowing agent-containing polymer melt.

In the second mixing zone for mixing the polymer melt containing the blowing agent and the polymer melt containing the additive, the screw machine is particularly provided with a cooling section. If necessary, the cooling section allows at least some of the mechanical energy introduced during mixing to be removed again from the additive/blowing agent-containing polymer melt. The temperature of the polymer melt containing the additive/blowing agent is preferably measured with a temperature sensor in the second mixing zone and monitored with a control device.

Another object of the present invention is to provide an apparatus that makes it possible to prepare a polymer melt containing an additive/blowing agent in a simple manner.

This object is achieved with an apparatus for producing a polymer melt containing an additive/blowing agent, the apparatus comprising a screw machine, the screw machine comprising a casing; At least one casing bore formed in the casing; At least one processing element shaft disposed within the casing bore; A first feed port that opens into the at least one casing bore to provide a first polymer melt; A second feed port for feeding at least one additive, which feed port is disposed downstream of the first feed port with respect to the delivery direction and passes toward the at least one casing bore; A first mixing zone for mixing the at least one additive and the first polymer melt to obtain an additive-containing polymer melt; A third supply port for supplying a polymer melt containing a blowing agent, the third supply port being disposed downstream of the first mixing region with respect to the delivery direction and through the at least one casing bore; A second mixing zone for mixing the blowing agent-containing polymer melt and the additive-containing polymer melt to obtain an additive/blowing agent-containing polymer melt; And a mixing device opened into the third feed port to mix at least one blowing agent into the second polymer melt to provide a blowing agent-containing polymer melt. The advantages of the device according to the invention correspond to the advantages of the method according to the invention already described above. Thus, the device according to the invention can be further refined in particular to have the features according to the invention.

The mixing device is through a third feed port toward the screw machine, so that the provided blowing agent-containing polymer melt is mixed with the additive-containing polymer melt in a second mixing zone to form an additive/blowing agent-containing polymer melt. The first polymer melt is provided through a first feed port. According to the first method, this is done by feeding polymer pellets (melted in the melting zone to obtain a first polymer melt) through the first feed port into the screw machine. In a second method, the first polymer melt is fed through a first feed port and delivered to the first mixing zone through a screw machine. The first polymer melt is, for example, taken from the polymerization reactor and delivered to the first feed by a melt pump. Preferably, a melt cooler, in particular a static melt cooler, is arranged between the melt pump and the first feed port to cool the first polymer melt. In the third method, the blowing agent-containing polymer melt provided by the mixing device is divided into a first partial flow and a second partial flow. By means of a melt pump, a first partial stream is conveyed into the screw machine through a first feed port, where the volatile components are liquefied in the discharge zone, ie at least one blowing agent is removed from the first partial stream. The first polymer melt is provided by removing volatile components from the blowing agent-containing polymer melt.

Through the second feed port, at least one additive is delivered into the screw machine and mixed with the first polymer melt in a first mixing zone disposed downstream thereof. The at least one additive is preferably added by means of a feeding device. This feeder is in particular a feed screw machine, in particular a double shaft side feed machine.

The screw machine preferably consists of a multi-screw machine, in particular a double-screw machine, which rotates together in close engagement with each other. This screw machine in particular has at least one cooling section for cooling the first polymer melt and/or the additive-containing polymer melt and/or the additive/blowing agent-containing polymer melt. Preferably, the screw machine has at least one temperature sensor for measuring the temperature of the first polymer melt and/or the additive-containing polymer melt and/or the additive/blowing agent-containing polymer melt. This at least one temperature sensor is in particular arranged in the first mixing zone and/or the second mixing zone. The screw machine also has a control device which is used in particular to monitor the temperature of the first polymer melt and/or the additive-containing polymer melt and/or the additive/blowing agent-containing polymer melt.

Preferably, a melt cooler for cooling the additive/blowing agent-containing polymer melt and a pelletizer for pelletizing the cooled additive/blowing agent-containing polymer melt are arranged downstream of the screw machine. Moreover, preferably at least one melt pump is arranged downstream of the screw machine. The at least one melt pump is arranged between the screw machine and the melt cooler and/or between the melt cooler and the pelletizer.

The at least one processing element shaft provides a simple way for a device having at least one first accumulating member upstream of the second feed port to mix at least one additive to form a first accumulating region of the first polymer melt. The at least one first accumulating member has a delivery direction opposite to that of the screw machine. The first polymer melt accumulates in the first accumulation region so that the first polymer melt forms a melt seal. This melt seal prevents volatile components exiting the additive-containing polymer melt from flowing upstream toward the first feed port. Preferably, downstream of the at least one first accumulating member, the screw machine has an outlet through which volatile components can escape.

The at least one processing element axis is a device having at least one second accumulating member between the second supply port and the third supply port to form a second accumulation region of the additive-containing polymer melt, comprising a blowing agent-containing polymer melt and an additive. It provides a simple way to mix the polymer melt. The at least one second accumulating member has a delivery direction opposite to that of the screw machine. The additive-containing polymer melt accumulates in the second accumulation region so that the polymer melt forms a melt seal upstream of the third feed port, ie between the second feed port and the third feed port. This melt seal prevents the blowing agent from flowing in the upstream direction from the blowing agent-containing polymer melt, where the blowing agent can escape from the screw machine through an outlet and/or a supply port.

An outlet is formed in the casing between the at least one first accumulating member and at least one second accumulating member, and this outlet in particular provides a simple way for a device arranged upstream of the second supply to mix at least one additive. to provide. Volatile components that escape from the additive-containing polymer melt while the at least one additive is being mixed can easily escape through the outlet. The evacuation is in particular carried out by a rear evacuation process. Therefore, the outlet is arranged in particular upstream of the second supply port.

The mixing device includes a melt cooler; A polymer supply line for supplying a second polymer melt to the melt cooler; And a blowing agent supply line for supplying at least one blowing agent, wherein the blowing agent supply line is in particular open into the melt cooler to provide a simple way to prepare a blowing agent-containing polymer melt. The second polymer melt is delivered to the cooled melt through a polymer supply line. To this end, the apparatus preferably has a melt pump arranged between the polymerization reactor and the melt cooler for transferring the second polymer melt from the polymerization reactor to the melt cooler. The blowing agent supply line is used to supply at least one blowing agent to the second polymer melt. For this purpose, the blowing agent supply line is opened into the polymer supply line and/or the melt cooler. The melt cooler is preferably a static melt cooler and includes a cooler casing in which the static mixture is disposed. In order to cool the polymer melt containing the blowing agent, the cooler casing is provided with a cooling member. The mixing device provides a simple way to prepare a cooled blowing agent-containing polymer melt. The melt cooler can introduce relatively high cooling power to the blowing agent-containing polymer melt.

A polymerization reactor for providing a second polymer melt is disposed upstream of the mixing device, and in particular an apparatus in which a melt pump is disposed between the polymerization reactor and the mixing device provides a simple way of preparing the second polymer melt. The second polymer melt is fed from the polymerization reactor to the mixing device. To feed the second polymer melt, a melt pump is in particular arranged between the polymerization reactor and the mixing device, allowing the second polymer melt to be fed to the mixing device at a high melt pressure. This ensures complete mixing of the second polymer melt with the at least one blowing agent.

Other features, advantages, and details of the present invention will become apparent from the following description of various embodiments.

1 shows a schematic diagram of an apparatus for producing a polymer melt containing an additive/blowing agent according to a first embodiment.
FIG. 2 shows a cross-sectional view of the screw machine taken along line II-II in FIG. 1.
3 shows a schematic diagram of an apparatus for producing a polymer melt containing an additive/blowing agent according to a second embodiment.
4 shows a schematic diagram of an apparatus for producing an additive/blowing agent-containing polymer melt according to a third embodiment.

Hereinafter, a first exemplary embodiment of the present invention will be described with reference to FIGS. 1 and 2. Figure 1 shows an installation 1 for the production of polymer pellets (P _G). This facility (1) comprises _{a device (2) for the production of a polymer melt (P AT} ) containing additives/blowing agents, a melt pump (4) downstream of the device in the delivery direction (3), and a static melt cooler. (5), another melt pump 6 and a pelletizer 7 are arranged.

The device 2 comprises a double shaft screw machine 8. This screw machine 8 has a casing 9 formed with two casing bores 10 and 10' overlapping each other, which are in the form of the number 8, which is horizontally overturned when viewed in cross section. In the casing bore 10, 10', two processing element shafts 11, 11' are arranged so as to be concentric with the associated axis of rotation 12, 12'. The processing element shafts 11, 11' are adapted to rotate in the same direction and closely engage each other. The processing element shafts 11 and 11 ′ are driven by an electric drive motor 13 via a reduction/distribution gear box 14 installed in the casing 9. The treatment element shafts 11, 11' have shafts 24, 24' provided with several treatment elements arranged in pairs before and after each other. Its processing elements will be described in detail below.

Viewed from the delivery direction (3), the screw machine (8) has an inlet region (15), a melting region (16), a first accumulation region (17), a first mixing region (18) and a second accumulation, which are arranged back and forth from each other It has a region 19, a second mixing region 20 and a discharge region 21.

In the inlet region 15, a first supply port 22 is formed in the casing 9, and the supply port 22 allows the polymer pellets P to be supplied through the hopper-type material inlet 23. Do it. In the inlet region 15, the screw members 25 are arranged in a non-rotating manner on the shafts 24, 24', these screw members 25 moving the polymer pellets P in the direction of the melting region 16. Will be delivered.

Shafts 24 and 24' in the melting zone 16 are provided with a non-rotating kneading and/or screw member 26 required to melt the polymer pellets P. In the melting process, a first polymer melt P ₁ provided at the end of the melting region 16 is produced. In order to measure the temperature T ₁ of the first polymer melt P ₁ , the first temperature sensor 27 is disposed in the casing 9 in the melting region 16. The screw machine 8 also has a first cooling part 28 in the melting zone 16, which is a cooling duct in the casing 9.

The first accumulation region 17 is formed of a first accumulation member 29 non-rotatingly disposed on the shafts 24 and 24'. This first accumulating member 29 has a delivery direction opposite to the delivery direction 3. Thereby, the first polymer melt P ₁ can accumulate to form a melt seal. The first accumulating member 29 is in particular made of a screw member having a pitch opposite to that of the screw member 25.

In the first mixing region 18, a second supply port 30 is formed in the casing 9, through which at least one additive A can be supplied into the casing 9. At least one additive (A) is supplied by means of a feeding device. This feeding device 31 is a screw machine. The feeding device 31 is preferably a double shaft side dosing machine. The design of this kind of supply device 31 is known. The feed device 31 is opened through the second feed port 30 into the casing bore 10, 10 ′. The feeding device 31 delivers at least one additive A in the feeding direction 58. Shafts 24, 24' are provided with non-rotating kneading and/or screw elements 32 in the mixing zone 18 for mixing at least one additive (A) with the first polymer melt (P _{1 ).} . When at least one additive (A) is _{mixed with the first polymer melt (P 1} ), an additive-containing polymer melt (P _A ) is obtained. In the mixing zone 18, the casing 9 is provided with an outlet 33, which allows the volatile components to escape from the _{additive-containing polymer melt P A during mixing.} The additive-containing polymer melt (P _A ) is removed from volatile components during the rear discharge process. To this end, the outlet 33 is disposed between the accumulation region 17 or the accumulation member 29 and the second supply port 30. In the first mixing region 18, the second temperature sensor 34 is disposed in the casing 9 to measure the temperature T _{2 of the additive-containing polymer melt P A.} The screw machine 8 further has a second cooling section 35 in the first mixing zone 18. This second cooling part 35 is in the form of a cooling duct disposed in the casing 9.

In the second accumulation region 19, the second accumulation member 36 is disposed non-rotationally on the shafts 24 and 24'. Corresponding to the first accumulating member 29, the second accumulating member 36 has a conveying direction opposite to the conveying direction 3. Thereby, the additive-containing polymer melt P _A is accumulated so that a melt seal is formed in the second accumulation region 19.

In the second mixing region 20, a third supply port 37 is formed in the casing 9, through which the blowing agent-containing polymer melt P _T can be supplied into the casing 9 . The third feed port 37 is through the casing bore 10, 10 ′ at the upstream end of the second mixing zone 20. In the second mixing zone 20, the shafts 24, 24 ′ are provided with non-rotating kneading and/or screw elements 38. By this non-rotating kneading and/or screw member 38, the additive-containing polymer melt P _A is mixed with the blowing agent-containing polymer melt P _T in the second mixing region 20. The third temperature sensor 40 is disposed in the supply line 39 to measure the temperature T _{3 of the blowing agent-containing polymer melt P T.} The supply line 39 connects the mixing device 41 and the third supply port 37. In the second mixing region 20, the fourth temperature sensor 42 is disposed in the casing to measure the temperature T _{4 of the polymer melt P AT containing the additive/blowing agent.} The screw machine 8 further has a third cooling section 43 in the second mixing zone 20. This third cooling unit 43 is in the form of a cooling duct disposed in the casing 9.

In the discharge area 21, the screw machine 8 has a nozzle plate 44 comprising a discharge port 45. Its outlet 45 allows the additive/blowing agent-containing polymer melt (P _AT ) to be discharged from the screw machine 8.

The mixing device 41 is used to mix the at least one blowing agent (T) and the second polymer melt (P _{2 ).} To this end, the mixing device 41 has a static melt cooler 46 including a cooler casing 47, in which a static mixture 48 is disposed. The cooler casing 47 is provided with a cooling member 49 for cooling the blowing agent-containing polymer melt P _T. A blowing agent supply line 50 for supplying at least one blowing agent T is opened at the upstream end of the melt cooler 46 into the melt cooler. In addition, a polymer supply line 51 is opened into the melt cooler 46 at the upstream end. The polymer supply line is used to supply _{the second polymer melt P 2.}

In order to provide a second polymer melt P ₂ , the device 2 has a polymerization reactor 52 which is connected to the mixing device 41 via a melt pump 53.

The device 2, strictly speaking screw machine 8, is connected to a melt pump 4 and a static melt cooler 5 to pelletize the _{polymer melt P AT containing additive/blowing agent.} Corresponding to the melt cooler 46, the static melt cooler 5 has a cooler casing 54 comprising a static mixture 55 and a cooling member 56. The cooled additive/blowing agent-containing polymer melt (P _AT ) can be delivered to the pelletizer 7 by the melt pump 6. This pelletizer 7 is, for example, an underwater pelletizer or a water ring pelletizer. The pelletizer 7 is used to make inflatable or already expanded polymer pellets (P _G ).

A control device 57 is provided to control the facility 1 or device 2. This control device 57 is in particular in signal connection with the screw machine 8 and the associated temperature sensors 27, 34, 42 and the mixing device 41 and the temperature sensor 40.

The function of the facility 1, strictly speaking, of the device 2 is as follows.

The first polymer melt P ₁ is provided by the screw machine 8 and the second polymer melt P ₂ is provided by the polymerization reactor 52. Polymer melts (P ₁ , P ₂ ) are, in particular, melts composed of polystyrene, polypropylene, polyethylene, polylactide, cellulose acetate or mixtures of these polymers. Polymer melts (P ₁ , P ₂ ) are made of the same or different polymers.

In order to provide the first polymer melt P ₁ , non-expandable or expanded polymer pellets P are fed into the screw machine 8 via the first feed port 22, for example by means of a conventional metering device. By this screw machine 8, the polymer pellets P are transferred from the inlet region 15 to the melting region 16, where they are melted to form a first polymer melt P ₁ . The temperature T ₁ of this first polymer melt P ₁ is measured by a temperature sensor 27 and monitored by a control device 57. When the temperature (T _{1 ) of the first polymer melt (P 1} ) reaches an undesired excessive value as a result of the mechanical energy introduced by the screw machine (8) during the melting process, the control device (57) turns the cooling unit ( 28). The cooling unit 28 limits the temperature T ₁ of the first polymer melt P ₁ to a predetermined value. The temperature (T _{1 ) of the first polymer melt (P 1} ) at the downstream end of the melting zone (16), that is, before the at least one additive (A) is added, is T ₁ <185°C, in particular T ₁ It is <175°C, and particularly T ₁ <165°C. The melt pressure at the downstream end of the melting zone (16), strictly speaking the absolute pressure of the molten polymer melt (P _1), (p ₁₎ is p _1> 5 bar, in particular p ₁ > 10 bar, also in particular p ₁ > 15 bar.

In the first accumulation region 17, the first polymer melt P ₁ is accumulated by the first accumulation member 29 so that a melt seal is formed. _{The first polymer melt P 1} conveyed into the first mixing zone 18 is mixed there with at least one additive A to obtain an additive-containing polymer melt P _A. To this end, at least one additive A is delivered into the casing bore 10, 10 ′ through the second feed port 30 by means of a feed device 31. At least one additive (A) is mixed into _{the first polymer melt P 1} by means of a kneading and/or screw member 32. Volatile components that escape from the additive-containing polymer melt P _A during mixing may escape from the first mixing region 18 through the rear discharge port 33. The temperature T ₂ of the additive-containing polymer melt P _A is measured with a temperature sensor 34 during mixing. If necessary, the control device 57 operates the second cooling unit 35 according to the _{measured temperature T 2.} As a result, the temperature T ₂ is limited to a predetermined value. The temperature (T ₂ ) of the additive-containing polymer melt (P _{A ) is T 2} <195°C, in particular T ₂ <185°C, and in particular T ₂ <175°C. The melt pressure at the downstream end of the first mixing zone 18, i.e. the absolute melt pressure p _{2 of the additive-containing polymer melt P A} is in particular p ₂ > 5 bar, especially p ₂ > 10 bar, also in particular p ₂ > 15 bar. The at least one additive (A) is in particular selected from the group consisting of flame retardants, cell modifiers, graphite, carbon black, talc and colorants and treatment aids. The first accumulation region 17 allows volatile components to escape through the outlet 33 without continuing to flow in the upstream direction.

The additive-containing polymer melt P _A is accumulated by the second accumulating member 36 in the second accumulating region 19 so that a melt seal is formed. When the additive-containing polymer melt (P _A ) is mixed with the blowing agent-containing polymer melt (P _T ), the melt seal prevents the volatile blowing agent (T) from flowing through the screw machine 8 in the upstream direction. The volatile blowing agent may escape through the second supply port 30 or the discharge port 33 in an undesired manner.

In order to provide the blowing agent-containing polymer melt (P _T ), the second polymer melt (P ₂ ) is transferred from the polymerization reactor (52) via the polymer supply line (51) to the mixing device (41) by the melt pump (53). Is passed on. The second polymer melt P ₂ has a temperature of at most 300° C., in particular at most 280° C., and in particular at most 260° C. when exiting the polymerization reactor 52. The second polymer melt P ₂ is mixed with at least one blowing agent T in the melt cooler 46. To this end, at least one blowing agent T is supplied into the melt cooler 46 through the blowing agent supply line at the downstream end of the blowing agent supply line 50. The static mixture 48 mixes the second polymer melt P ₂ and at least one blowing agent T, and at the same time, the blowing agent-containing polymer melt P _T is cooled by the cooling member 49. When discharged from the melt cooler 46, the temperature T _{3 of the polymer melt P T} is measured by the temperature sensor 40. The control device 57 cools the cooling member 49 according to the _{measured temperature T 3} so that the temperature T ₃ has a predetermined value. Immediately before or during the feeding into the screw machine 8, the temperature T ₃ is T ₃ <180°C, in particular T ₃ <170°C, and in particular T ₃ <160°C. During the supply of the blowing agent-containing polymer melt (P _T ), the melt pressure or absolute melt pressure (p ₃ ) is in particular p ₃ > 1 bar, especially p ₃ > 3 bar, also in particular p ₃ > 5 bar.

The at least one blowing agent (T) is selected from the group comprising hydrocarbons such as n-pentane and iso-pentane, carbon dioxide, nitrogen and mixtures thereof. At least one blowing agent (T) is added in a liquid and/or gaseous state. When at least one blowing agent (T) is added, the _{viscosity and temperature of the second polymer melt (P 2} ) are lowered, so that mixing of the at least one blowing agent (T) in the mixing device 41 is facilitated.

The blowing agent-containing polymer melt P _T is fed into the casing bore 10, 10 ′ through the third feed port 37 at the upstream end of the second mixing region 20. The additive-containing polymer melt P _A is mixed with the blowing agent-containing polymer melt P _T by means of a kneading and/or screw member 38. The melt seal formed in the second accumulation region 19 prevents the volatile blowing agent (T) escaping from the _{polymer melt (P T) containing the blowing agent from flowing in the upstream direction during the mixing process, and the blowing agent can escape from the upstream.} have. The temperature (T ₄ ) of the additive/blowing agent-containing polymer melt (P _AT ) is measured with a temperature sensor 42. If necessary, the control device 57 operates the third cooling unit 43 according to the _{measured temperature T 4.} In order that the temperature (T ₄ ) in the second mixing region 20 is limited to a predetermined value, the cooling unit 43 is at least one of the mechanical energy introduced into the _{additive/blowing agent-containing polymer melt (P AT) during the mixing process.} You will remove the part. T ₄ is T ₄ <240°C, particularly T ₄ <210°C, and particularly T ₄ <180°C. The melt pressure at the downstream end of the second mixing zone 20, strictly speaking, the absolute melt pressure (p _{4 ) of the additive/blowing agent-containing polymer melt (P AT} ) is in particular p ₄ > 25 bar, in particular p ₄ > 30 bar, also in particular p ₄ > 35 bar.

The polymer melt P _AT is discharged from the screw machine 8 through the outlet 45. Upon exiting the screw machine 8, the polymer melt P _AT is delivered into the static melt cooler 5 by the melt pump 4 at a pressure of 70 to 300 bar. In this melt cooler 5, the polymer melt P _AT is cooled to have a temperature of less than 190° C., in particular less than 180° C., and in particular less than 170° C. downstream of the melt cooler 5. By the cooling process, _{the viscosity of the polymer melt (P AT} ) increases again, that is, the decrease in viscosity due to the at least one blowing agent (T) added is at least partially compensated. When discharged from the melt cooler 5, the cooled polymer melt (P _AT ) is supplied to the pelletizer 7 by the melt pump 6 at a pressure of 70 to 300 bar, where it is pelletized in a conventional manner, Polymer pellets (P _G ) are obtained from the polymer melt (P _{AT ).} Depending on the type of the polymer melt (P ₁ , P ₂ ) and at least one blowing agent (T) selected, expandable polymer pellets (P _G ) and expanded polymer pellets may be prepared according to the pelletizing method. The expandable polymer pellets (P _G ) are preferably produced by an underwater pelletizing process, and the expanded polymer pellets (P _G ) are preferably produced by a water ring pelleting process.

The additive/blowing agent-containing polymer melt (P _AT ) has a polymer weight ratio (a _s ). The polymer weight ratio of (a _s) is comprised of a first polymer weight ratio (a ₁₎ and the second polymer weight ratio (a ₂₎ of a second polymer melt (P ₂₎ of a first polymer melt (P _1), a _s = a ₁ + a ₂ to be. A first polymer weight ratio of the polymer melt (P ₁₎ (a ₁₎ is a ₁ <0.4·a _S , especially a ₁ <0.3·a _S , also in particular a ₁ <0.2·a _S. Therefore a ₂ /a ₁ Rain is a ₂ /a ₁ > 3/2, especially a ₂ /a ₁ > 7/3, also especially a ₂ /a ₁ >4. Thus, the first polymer melt (P ₁ ) has a first polymer weight ratio (a ₁ ) that is smaller than the second polymer melt (P ₂ ) with an associated polymer weight ratio (a _{2 ).} By continuously mixing at least one additive (A) and the first polymer melt (P ₁ ) and also mixing the resulting additive-containing polymer melt (P _A ) and the blowing agent-containing polymer melt (P _T ) thus obtained. , The additive/blowing agent-containing polymer melt (P _AT ) is easily prepared. Since only the polymer weight ratio (a ₂ ) flows through the melt cooler 46, the melt cooler 46 can be configured to have a relatively small size.

The apparatus 2 according to the invention and the method according to the invention, wherein the additive-containing polymer melt (P _A ) and the additive/blowing agent-containing polymer melt (P _AT ) are at a critical decomposition temperature of at least one additive (A) during manufacture Do not exceed (T _{K ). The critical temperature (T K} ) of the at least one additive is in particular T _K ≥ 180°C, in particular T _K ≥ 210°C, and in particular T _K ≥ 240°C. The device 2 according to the invention also ensures a high throughput.

Hereinafter, a second exemplary embodiment of the present invention will be described with reference to FIG. 3. Unlike the first exemplary embodiment, the first polymer melt P ₁ is provided by the polymerization reactor 59. By the melt pump 60, the first polymer melt P ₁ is delivered to the melt cooler 61 at a pressure of 70 to 300 bar. This melt cooler 61 is a static melt cooler, and thus has a cooler casing 62 comprising a static mixture 63 corresponding to the melt coolers 5 and 46. A cooling member 64 is provided to cool the first polymer melt P ₁ . The melt cooler 61 is opened into the first feed port 22 via the polymer feed line 65. Since the melting process can be omitted due to the supply of the melt, the inlet region 15 reaches the first accumulation region 17. A temperature sensor 27 and a cooling device 28 are arranged in the inlet region 15. Alternatively, the temperature sensor 27 can also be arranged in the polymer supply line 65. The cooling device 28 can be omitted if the cooling provided by the melt cooler 61 is sufficient. Upon exiting the polymerization reactor 59, the first polymer melt P ₁ has a temperature of at most 300°C, in particular at most 280°C, and in particular at most 260°C. For cooling, the first polymer melt P ₁ is delivered to the melt cooler 61 at a pressure of 70 to 300 bar by the melt pump 60. When discharged from the melt cooler 61, the first polymer melt P ₁ has a temperature T ₁ . Downstream of the melt cooler 61, the melt pressure p ₁ is p ₁ > 1 bar, especially p ₁ > 3 bar, also in particular p ₁ > 5 bar. Alternatively, the first polymer melt P ₁ and the second polymer melt P ₂ may be taken from a common polymerization reactor 52. In this case, a common melt pump 60 or 53 is used to supply _{the first polymer melt P 1} to the melt cooler 61 and to supply the second polymer melt P _{2 to the melt cooler 46.} I can. Other structural and functional details of the installation 1 and the apparatus 2 are described in the description of the previous embodiment.

Hereinafter, a third exemplary embodiment of the present invention will be described with reference to FIG. 4. Unlike the previous embodiments, the apparatus 2 has _{a supply line 66 for supplying the blowing agent-containing polymer melt P T} to the first supply port 22, and the supply of the blowing agent-containing polymer melt is This is done by a melt pump 67 arranged in the supply line 66. The feed line 66 runs from the melt cooler 46 or feed line 37 to the first feed port 22, which feed line is open into its first feed port. Due to the supply of the melt, the melting process and the melting region can be omitted, so that the inlet region 15 reaches the first accumulation region 17. In order to provide the first polymer melt P ₁ , an outlet 68 is formed in the inlet region 15 of the casing 9. At least one blowing with a blowing agent contained poly said melt (P _T), the (T) is because the volatile blowing out from that containing the said molten polyester (P _T) is discharged out through said discharge opening (68). The discharge process is preferably a rear discharge process. Therefore, the outlet 68 is formed in the casing 9 upstream of the first supply port 22. At the downstream end of the inlet region 15, the at least one blowing agent T completely exits and a first polymer melt P ₁ is provided. When the cooling provided by the melt cooler 46 is sufficient, the cooling unit 28 may be omitted. Thus, the blowing agent-containing polymer melt (P _T ) is divided into two partial streams. A small first partial flow is transmitted through the first feed port 22 and the volatile components are removed in the screw machine 8 to obtain a first polymer melt P ₁ . Corresponding to the preceding embodiments, the second partial flow is passed into the screw machine 8 through the third feed port 37, where it is mixed with the _{additive-containing polymer melt P A.} As another effect of removing volatile components, the melt temperature decreases so that the first polymer melt P ₁ has a temperature T ₁ . Other structural and functional details of the installation 1 and the apparatus 2 are described in the description of the previous embodiment.

The apparatus 2 according to the invention and the method according to the invention consist of a one-stage design. Due to this once design, only one screw machine 8 is required to mix at least one additive (A) and at least one blowing agent (T). Prior to mixing the additive-containing polymer melt (P _A ) and the blowing agent-containing polymer melt (P _t ), the at least one additive (A) and the at least one blowing agent are separately from each other, the polymer melt (P ₁ ) and the polymer melt (P ₂ ) Since each is mixed in, the additive/blowing agent-containing polymer melt (P _AT ) can be prepared in a simple and flexible manner while ensuring high throughput. The additive-containing polymer melt (P _A ) or the additive/blowing agent-containing polymer melt (P _AT ) does not exceed _{the decomposition temperature (T K} ) of the at least one additive (A). As another advantage provided by the apparatus 2 according to the invention and the method according to the invention, the _{mechanical energy input required to prepare the polymer melt (P AT} ) is optimized, so that the required cooling process can be optimized and also the critical decomposition It is possible to prevent the temperature (T _{K) from being exceeded.}

Claims (19)

As a method for preparing a polymer melt containing an additive/blowing agent,
-Providing a first polymer melt (P ₁ ) and a second polymer melt (P ₂ );
-Mixing at least one additive (A) and said first polymer melt (P ₁ ) with a screw machine (8) to obtain an additive-containing polymer melt (P _{A );}
-Mixing at least one blowing agent (T) and the second polymer melt (P ₂ ) to obtain a blowing agent-containing polymer melt (P _{T );}
-Adding the blowing agent-containing polymer melt (P _T ) to the additive-containing polymer melt (P _{A) provided in the screw machine (8);} And
-Mixing the blowing agent-containing polymer melt (P _T ) and the additive-containing polymer melt (P _A ) with the screw machine (8) to obtain an additive/blowing agent-containing polymer melt (P _{AT ).} , A method for preparing a polymer melt containing an additive/blowing agent. The method of claim 1,
The additive/blowing agent-containing polymer melt (P _AT ) has a polymer weight ratio (a _s ). First polymer weight ratio (a ₁₎ of the first polymer melt (P ₁₎ is a ₁ A method for producing a polymer melt containing an additive/blowing agent, characterized in that <0.4· _aS. The method of claim 1,
Before adding the at least one additive (A), the first polymer melt (P ₁ ) has a temperature (T ₁ ), and this temperature (T ₁ ) is T ₁ A method for producing a polymer melt containing an additive/blowing agent, characterized in that it is <185°C. The method of claim 1,
Additive/blowing agent containing, characterized in that prior to mixing the at least one additive (A) with the screw machine (8), the first accumulation region (17) is _{formed from the first polymer melt (P 1 ).} A method for making a polymer melt. The method of claim 1,
_A method for producing an additive/blowing agent-containing polymer melt, characterized in that during mixing the at least one additive (A), the volatile component is liquefied in the additive-containing polymer melt (P A ). The method of claim 1,
Before adding the blowing agent-containing polymer melt (P _T ), the additive-containing polymer melt (P _A ) has a temperature (T ₂ ), and this temperature (T ₂ ) is T ₂ A method for producing a polymer melt containing an additive/blowing agent, characterized in that it is <195°C. The method of claim 1,
After mixing the at least one additive (A) and _{before adding the blowing agent-containing polymer melt (P T} ), a second accumulation region (19) is formed by means of the screw machine (8) to form the additive-containing polymer melt ( _A method for preparing a polymer melt containing an additive/blowing agent, characterized in that it is formed of P A ). The method of claim 1,
When fed into the screw machine 8, the blowing agent-containing polymer melt (P _T ) has a temperature (T ₃ ), and this temperature (T ₃ ) is T ₃ A method for producing a polymer melt containing an additive/blowing agent, characterized in that it is <180°C. The method of claim 1,
Method for producing an additive/blowing agent-containing polymer melt, characterized in that the blowing agent-containing polymer melt (P _{T) is cooled before being fed into the screw machine (8).} The method of claim 9,
The method for producing an additive/blowing agent-containing polymer melt, characterized in that the blowing agent-containing polymer melt (P _{T) is cooled by a melt cooler (46).} An apparatus for producing a polymer melt containing an additive/blowing agent, the apparatus comprising a screw machine (8), the screw machine comprising:
-Casing 9;
-At least one casing bore (10, 10') formed in the casing (9);
-At least one processing element shaft (11, 11') arranged in said casing bore (10, 10');
-A first feed port 22 that opens into said at least one casing bore 22 to provide a first polymer melt P _1;
-A second supply port 30 for supplying at least one additive (A)-The supply port 30 is disposed downstream of the first supply port 22 with respect to the delivery direction 3 and the at least one Through the casing bore (10, 10') of the -;
-A first mixing zone 18 for mixing said at least one additive (A) and said first polymer melt (P ₁ ) to obtain an additive-containing polymer melt (P _{A );}
-A third supply port (37) for supplying a polymer melt (P _T ) containing a blowing agent-The third supply port (37) is downstream of the first mixing region (18) with respect to the delivery direction (3). Arranged and through the at least one casing bore (10, 10');
-A second mixing zone 20 for mixing the blowing agent-containing polymer melt (P _T ) and the additive-containing polymer melt (P _A ) to obtain an additive/blowing agent-containing polymer melt (P _{AT );} And
-Mixing device (41) through the third supply port (37) to provide the blowing agent-containing polymer melt (P _T ) by mixing at least one blowing agent (T) into the second polymer melt (P _{2 ).} ), an apparatus for producing a polymer melt containing an additive/blowing agent. The method of claim 11,
The at least one processing element shaft (11, 11 ′) is at least one secondary upstream of the second supply port (30) to form a first accumulation region (17) with _{the first polymer melt (P 1 ).} 1 apparatus for producing an additive/blowing agent-containing polymer melt, characterized in that it has an accumulating member (29). The method of claim 11,
The at least one processing element shaft (11, 11 ′) is provided with the second feed port 22 and the third feed port for forming a second accumulation region 19 _{with the additive-containing polymer melt P A} 30) Apparatus for producing a polymer melt containing additive/blowing agent, characterized in that it has at least one second accumulating member (36) therebetween. The method of claim 12,
The at least one processing element shaft (11, 11 ′) is provided with the second feed port 22 and the third feed port for forming a second accumulation region 19 _{with the additive-containing polymer melt P A} 30) between the at least one second accumulating member (36), and between the at least one first accumulating member (29) and at least one second accumulating member (36) in the casing (9) with an outlet (33). ) Is formed, an apparatus for producing a polymer melt containing an additive/blowing agent. The method of claim 14,
Device for producing a polymer melt containing additive/blowing agent, characterized in that the outlet (33) is arranged upstream of the second supply port (30). The method of claim 11,
The mixing device 41,
-Melt cooler 46;
-A polymer supply line 51 for supplying the second polymer melt P _{2 to the melt cooler 46;} And
-An apparatus for producing a polymer melt containing an additive/blowing agent, characterized in that it comprises a blowing agent supply line (50) for supplying at least one blowing agent (T). The method of claim 16,
The apparatus for producing an additive/blowing agent-containing polymer melt, characterized in that the melt cooler (46) consists of a static melt cooler, and the blowing agent supply line (50) passes through the static melt cooler side. The method of claim 11,
A device for producing a polymer melt containing an additive/blowing agent, characterized in that a polymerization reactor (52) for providing a second polymer melt (P _{2) is arranged upstream of the mixing device (41).} The method of claim 18,
A device for producing a polymer melt containing an additive/blowing agent, characterized in that a melt pump (53) is arranged between the polymerization reactor (52) and the mixing device (41).

Images